Cowl for air-cooled internal-combustion engines for aircraft



y 1951 B. G. MARKHAM ET AL 2,558,865

COWL FOR AIR-COOLED INTERNAL-COMBUSTION ENGINES FOR AIRCRAFT Filed Sept. 29, 1947 4 Sheets-Sheet 1 //VV/V7'05 5.4511 ca: MAEZHAM 50006245 J ZEN/Vi y 3, 1951 G. MARKHAEJIIRN AL 2,558,865

COWL FO IR-COOLED INT COMBUSTION ENGINES FOR AIRCRAFT Filed Sept 29, 1947 4 Sheets-Sheet 2 mlllurfl July 3, 1951 B MARKHAM ETAL 2,558,865

COWL FOR AIR-COOLED INTERNAL-COMBUSTION ENGINES FOR AIRCRAFT Filed Sept. 29, 1947 4 Sheets-Sheet 3 B4511. c; MAE/(6AM 176016 JAM/m 21 J4 INVf/VTORS y 1951 B. G. MARKHAM ET AL COWL FOR AIR-COOLED INTERNAL-COMBUSTION ENGINES FOR AIRCRAFT Filed Sept. 29, 1947 4 Sheets-Sheet 4 Z/Vl/[MO/PS BASZ G WHY/4M i DOUGLAS JAE/WATY b m a. a

Patented July 3, 1951 'UNITED STATES PATENT OFFICE COWL or; "AIR-COOLED INTERNAL-COM- --BUSTION ENGINES FOR AIRCRAFT Basil Gervase -Markharn--- and --Douglas John Kenney, --Bristol, England, assignors to The Bristol-Aeroplane Company Limited, Bristol,

England, a 'Britishcompany Application September 29;1947, Serial N o. 776;656 In GreatBritain September'ZG, 1946 Section 1, Public Law*690, August 8, 1946 Patent expires September 26, 1966 2 Claims. 1

This invention concerns cowls for air-cooledin tcrnal combustion engines for'aircraft.

The pressure existing at the leading edge-of 'Wings having considerable depth "(that is, so

" called thick-section wings) is positive and "of "some considerable value. In air cooled engine'installations carried on the leading-edge of such wings it is common practice to direct'all the coo1- ing air from the cowl through a single exit and to'dispose'the latter'at a point adjacent the lead ing-edge of the wing. With such an arrangement the pressures prevailing 'at the leading edge of th'e'wing and the'eXit from the co'wl are such'as to prevent a proper fiow'of air through the cowl; "as a'result'the cooling effect on the engine is reduced.

According to one feature of the'present invention a cowl for an air-cooled internal'combustion enginefor aircraft ischaracterised in that the stream of cooling air entering the co'wlisdivided' into'two streams, one 'of which is adapted to flow over the upper part and the other over the lower partof' the cylinders, and in that two outlets are provided for the cooling air, said outlets being spaced along the length of the cowl and one being provided for'each stream of cooling air.

Accordingto another feature of the present invention a cowl for an air-cooled internal combus- 1 tionengine mounted on the' leading edge of the wing of an aeroplane is characie-rised in that-the cooling air entering the cowl'is"divid'ed into two streams, one for the head and the other for-the barrels of the cylinder, and'in that eachstr'eam is separatelydischarged'from the cowl, the'cylim der-head stream'leaving the cowl through an opening situated between the entry and thedischarge for the cylinder-barrel streamand outside the positive pressure region at the leadingedge of the wing,

In-order that the nature of the invention may be fully understood a specific embodiment of the invention will now be described, by way of '2 Referring first of all to"Figure lfithenacelle which is generally indicatedby' the reference numeral 5 is carried inknownm'a'nnerby the wing 5 of the aeroplane (not'shown).' An engine I (Figure 2) is enclosed in a cowl'generally indicated'at 8 which'forms a part of the 'nacelle 5.

' The engine drives an airscrew 9 having a; spinner 'lfiz' the spinner contour is extendedrearw'ardly asat l I (Figure 2) and defines with thef10sel2 -oft-he cow} 8 an openingfltthr'ough which air passes. This air enters the cowl 8 and 'fiowsover U the'cylinders of the engine 'lto'c'ool the latter as later'described. "The air is forced throughjthe cowl by a fan i l'lying within theopeni'ng' l3 the fan being driven by the engine I. I The co'wl 8 comprises the nose I2; an inner cylindrical casing I5 and an outer'cylindrical'casing E6. The nose-"i2 is formed in'thi'ee"segmental parts each'of which is indepe'nden'tlyrerhovable so as to give access to the forward 'part'of the cowl. The outer casing 16 is built up from four segmental panels which are hinged to longitudinally-extending supports whereby the panels ma be opened togive access to the inner casing-l5. The latter" is formed in two parts which are removable to give access to the engine.

The inner casing'lii is formed with aplurality "of openings 1? so that the spacelt defined between the casings I5, [6 is placed in'cominunication with the engine space. One such opening is associated with each cylinderld of the engine I and there isat-tached to the leading-edge f each .opening a deflector plate -29. The latter, for in- .stance, is riveted'as'at ill to the'ca'sing-YIS a sealing' strip 22 being providedbetw'een the twofThe deflector plate lfi extends wholly across the cylinder and. downwardly into the junkhead; 23- (Figures 3 and 4). The-rear edge ofeach opening similarly supports a-defiector 2 l which is-downwardly-directedto engage with the flange of the -junkhead and extends from one outer edge of l the de fiectorplate zfi t0 the other.

With the arrangement described a' part of the --cooling-air entering the cowl 3 through the-open- :ing-J3- will be constrained -by=the deflector'zoto pass downwardly into the junkhead- 23 and thereafter to rise behind the deflector 2i? and will be directed by the plate 24 into the space 18. This flow of air is indicated by the arrow 25 of Fig ure 2.

Disposed at the rear edge of the casing I8 is a cowl ring 25 which is supported from the cylinders by means of rods 2? (Figure 2) and from the rear edge of the casing IE by a plurality of radial, spaced-apart arms 28 (Figure 3). There being discharged therefrom is 3 is thus defined between the rear edge of the casing [5 and the ring 26 an annular space 3| through which the cooling air passing along path 25 is discharged from the cowl 8.

The ring 26 is also spaced from the main part of the nacelle 5 so as to define an annular opening 29. Part of the cooling air entering the cowl 9 flows over the barrels of the cylinders l9 and directed rearwardly through the opening 29. This flow of air is indicated by the arrow:30 of Figure 2.

It will be appreciated that the cylinder barrels are each provided, in known manner, with cylinder baiiles which ensure that the cooling air is brought into intimate contact with the barrels.

It is clear from Figure 1 that the annular openings 29 and 3| 7 are spaced apart in the lengthwise direction of the nacelle 5 so that the cooling air flowing along the path 25 is discharged at a forward part of the cowl 9 and that the cooling air flowing along the path 39 is discharged at another and more rearwardly disposed part of the cowl.

From the above description it will be clear that the stream of cooling air entering the cowl 8 through the mouth I3 is divided into two parts one of which flows over the cylinder heads to cool the latter and then enters the space H; and is ejected in a rear direction from the annular exit 3|this is the part which follows the path indicated by arrow 25. Another stream passes over the cylinder barrels and flowing rearwardly through the cowl 8 is ejected through the second annular exit 29-this is the part which follows the path indicated by arrow 30.

With the construction described a considerable advantage is obtained when the aeroplane is powered by high-output engines and is operated at a low forward speed since under these rigorous conditions the engine cooling is ade-, quate and an improvement over previous constructions. This improvement is attributed to:

(a) there being an unrestricted outlet for the cooling air from the cylinder heads through the exit annulus 3|, the heads being the engine part which operates at the highest temperatures and thus requires greatest cooling,

(b) the proportion of the air used for cooling the cylinder heads being small relatively to the total amount of cooling air (about 15%) so that with a large area for exit 3| a low static pressure is created at said exit and the drag of the cowl is kept low,

(0) the relatively forward position of the annulus 3| so that it is in a position to avoid the high static pressure at the leading-edge of the wing 6; this forward disposition of the exit 3| is clear from Figure 1, and

(d) the air velocity in outlet 3| being relatively low so that the effects on the air flow of variations in exit static pressure around the circumference of the cowl will tend to be equalized resulting in more uniform cylinder head cooling.

A constructional advantage of the arrangement described is that considerable saving in weight is effected by the elimination of the controllable gills and operating mechanism therefor which are normallyv provided to control the flow of air through an aircraft cowl. This has the further advantage of eliminating the cockpit controls associated with the gill mechanism thereby relieving the pilot (or flight engineer) of the necessity of attending to them. The simplicity of the cowl and the entire absence of moving parts effect a considerable reduction in maintenance work and the reliability and life of the power plant are accordingly increased.

We claim:

1. In combination an air-cooled, sleeve-=valve internal combustion engine and a cowling therefor comprising an outer cylindrical casing to enclose the engine, there being an opening at the front end of the cowling through which all the cooling air for the engine enters and a main eXit at the rear end of the cowling for that part of the stream of cooling air which flows over the cylinder barrels, a deflector carried within the cowling to direct air from the intake opening of the cowling into the re-entrant opening in each engine cylinder head and a duct to convey air from the heads rearwardly within the cowling to an exit therefrom placed axially of the cowling between the engine cylinders and the main exit from the cowling.

2. An engine cowling combination according to claim 1 wherein the duct to convey air from the cylinder heads comprises an inner cylindrical casing within and spaced from the outer casing to form an annular duct passage which is closed at the front end of the cowl and open at the rear end thereof, a deflector plate for each cylinder carried b the inner casing and entering the reentrant opening in the cylinder head and means around an opening in the inner casing to seal the casing to each cylinder head, said opening lying downstream of the deflector plate and communicating with the re-entrant opening in the head, part of the cooling air entering the cowl being directed by the deflector plate into the reentrant openings in the cylinder head and passing therefrom into said annular passage.

BASIL GERVASE MARKHAM. DOUGLAS JOHN KENNEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

